As part of our investigation of the mechanism of estradiol-induced renal carcinogenesis in male Syrian hamsters, we have demonstrated that c-fos expression in tumor cells is high and regulated by estrogen binding to its receptor, whereas in kidney it is low and appears to be affected by estrogen metabolism, but not by receptor-mediated events. We intend to examine a hypothesis that flanking sequences of genes critical for cell transformation and tumor development are converted to estrogen-response elements by single mutations induced by estrogen metabolism. Thus, tumors may develop because genes, such as c-fos and c-myc, which are not affected by estrogen receptor-mediated events in kidney, are subjected to estrogen regulation and become overexpressed in estrogen-treated hamsters. We will examine our hypothesis by: 1a. determining the earliest time point at which c-fos expression becomes regulated by estrogen in kidneys of hamsters treated with estrogen for various lengths of time; 1b. examining the nature of c-fos expression by estrogen in H-301 tumor cells and in control renal interstitial cells to determine if c-fos expression requires protein or RNA synthesis, 2. sequencing flanking sequences of c-fos isolated from estrogen-induced tumor, from renal interstitial cells of hamsters treated with estrogen for various lengths of time, and from control renal interstitial cells; We will correlate the appearance of estrogen response elements with estrogen receptor-mediated c-fos expression in kidney of hamsters treated with estrogen. 3. studying the mechanism of conversion of a flanking sequence of c-fos to an estrogen response element by probing for the estrogen response element in renal interstitial cells of hamsters treated for various lengths of time with (i) estradiol plus antiestrogen, (ii) estradiol plus alpha-naphthoflavone, a cytochrome P450 IA1 inhibitor, which inhibits redox cycling of estrogens (iii) with weakly carcinogenic estrogens l7alpha-ethinylestradiol or 2- fluoroestradiol, or (iv) with estradiol as positive control; 4. studying the regulation of c-myc in tumors, in kidney of estrogen-treated hamsters, and in control kidney to find out whether c-myc is a second critical gene in kidney converted to an estrogen-regulated gene by treatment of hamsters with estradiol.